This invention relates to a multi-component substantially colorless marking liquid for use in a pressure-sensitive record material. More particularly, the invention relates to a reactive marking liquid which produces distinctive marks on properly sensitized record material by absorbing some or substantially all of the visible spectrum of light between a wavelength of 400 to 700 millimicrons.
Pressure-sensitive record materials employing colorless chromogenic compounds which form a mark when contacted with an acidic substance are well known in the art. Exemplary thereof are Crystal Violet Lactone (CVL) as described in Reissue patent No. 23,024 and the systems disclosed in U.S. Pat. Nos. 3,509,173 (3,3-bis(1-ethyl-2-methylindol-3-yl)phthalide, also known as Indolyl Red) and 3,681,390 (2'-anilino-3'-methyl-6'-diethylaminofluoran, also known as N-102 dye).
Liquid organic solvent solutions of the colorless chromogenic compounds are normally encapsulated and coated on the back side (CB) of sheets contained in a manifold record system. An acidic clay or resin is then coated on the front side (CF) of these sheets. When such sheets are placed in contiguous relationship, the microscopic rupturable capsules of colorless chromogenic compound from a mark upon capsule rupture and transfer and reaction of the capsule contents with the acidic material when pressure is applied thereto. Alternatively, the capsules of dye precursor or colorless chromogenic compound and acidic material may be coated on the same side of the record sheets, whereby the rupture of the capsules upon the application of pressure permits the admixture of the dye precursor with the acidic material and consequent mark formation.
The liquid solvent portion of the mark-forming liquid can be volatile or non-volatile and can constitute a single or multiple component solvent which is wholly or partially volatile. Some of the solvent system used in the prior art provide adequate print speed and color intensity on the widely used phenolic resin receiving sheets. However, certain of these prior art solvents are also known to cause problems, such as unsatisfactory retention of the ability of the CB sheet to produce an image of acceptable intensity after exposure of the CB coating to light. This reduction in ability to produce a satisfactory image after accelerated light exposure is called CB decline.
The chromogenic system itself is also, of course, critical in obtaining a satisfactory pressure-sensitive record material. Specifically, the mark formation must be intense and resistant to fade or change in color as well as being resistant to CB decline. Many of the prior art chromogenic systems are, however, prone to said CB decline.
As noted above, CVL has been widely used in commercially available carbonless copy paper systems. More recently, however, for a variety of reasons, the industry has been seeking new and alternative dye systems. These include compounds related to the Pyridyl Blue dye compound disclosed in the present application. For example, U.S. Pat. Nos. 3,775,424 and 3,853,869 of Farber disclose certain pyridine and pyrazine compounds which are closely related to Pyridyl Blue. Likewise, Japanese Kokai No. 75-05116 (Chem. Abstracts, Vol. 83, 3579v, 1975), Japanese Kokai No. 75-03426 (Chem. Abstracts, Vol. 83, 29895v, 1975) and Japanese Kokai No. 74-118515 (Chem. Abstracts, Vol. 82, 178280x, 1974) teach similar systems. However, none of these references teaches or suggests the critical proportions of dyes, solvents and other materials necessary for achieving the objectives of the present invention.
For instance, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, also known as TXIB, is an odorless, active solvent with acceptable toxicological properties. However, unless a major portion of CVL is replaced with Pyridyl Blue in the chromogenic system, or other materials are added, unacceptable results for CB decline tests are observed. Thus, one way to use TXIB successfully as a carbonless paper solvent in this context is to change the color former. Accordingly, as is shown below in Example 30, a color former containing Pyridyl Blue demonstrates a remarkable resistance to CB decline in a TXIB solvent.